Characterization of local immune responses associated with the parasitic resistance phenotype in morada nova lambs

Abstract

Brazil has great diversity of exotic sheep breeds and their crosses, as well as adapted breeds, like Morada Nova. However, gastrointestinal nematodes (GIN) are a major constrain in these production systems, specially Haemonchus contortus, prevalent species in the country. Morada Nova sheep, very adapted to tropical climate, are quite resistant to verminosis. Thus, the present study aims to characterize the parasitic resistance phenotype in lambs from the CPPSE Morada Nova flock, according to fecal egg counts (FEC), hematocrit and FAMACHA score. After two artificial infections with H. contortus L3, 20 animals (10 most resistant and 10 most susceptible) will be slaughtered for avaliation of the local immune response inducted by the parasite, by means of: (1) quantification of the expression immune response related genes (innate, pro-inflammatory, anti-inflammatory, regulatory T, humoral, Th1 profile and Th2 profile responses and complement system activation) in abomasum (fundic and pyloric regions) and abomasal lymph nodes, using RT-qPCR; (2) determination of IgG and IgA levels in abomasal mucus and (3) eosinophils and mast cell count in abomasal mucosa and submucosa. The identification of cytokines, cells and/or other mediators directly related to nematode resistance phenotype can be used to the improvement of the immune-prophylactic control of GIN infections. In the future, it would be possible to get mating generations, with homogeneous populations in relation to its composition, making it possible to offer resistant animals to producers, encouraging the use of Morada Nova sheep for meat production. (AU)